The present invention is concerned generally with minimally invasive vascular bypass surgery, and is directed to a catheterization methodology for creating a vascular bypass between an unobstructed artery or vein and an obstructed artery or vein in-vivo.
Coronary artery disease is the single leading cause of human mortality and is annually responsible for over 900,000 deaths in the United States alone. Additionally, over 3 million Americans suffer chest pain (angina pectoris) because of it. Typically, the coronary artery becomes narrowed over time by the build up of fat, cholesterol and blood clots. This narrowing of the artery is called arteriosclerosis; and this condition slows the blood flow to the heart muscle (myocardium) and leads to angina pectoris due to a lack of nutrients and adequate oxygen supply. Sometimes it can also completely stop the blood flow to the heart causing permanent damage to the myocardium, the so-called xe2x80x9cheart attack.xe2x80x9d
The conventional treatment procedures for coronary artery disease vary with the severity of the condition. If the coronary artery disease is mild, it is first treated with diet and exercise. If this first course of treatment is not effective, then the condition is treated with medications. However, even with medications, if chest pain persists (which is usually secondary to development of serious coronary artery disease), the condition is often treated with invasive procedures to improve blood flow to the heart. Currently, there are several types of invasive procedures: (1) Catheterization techniques by which cardiologists use balloon catheters, atherectomy devices or stents to reopen up the blockage of coronary arteries; or (2) Surgical bypass techniques by which surgeons surgically place a graft obtained from a section of artery or vein removed from other parts of the body to bypass the blockage.
Conventionally, before the invasive procedures are begun, coronary artery angiography is usually performed to evaluate the extent and severity of the coronary artery blockages. Cardiologists or radiologists thread a thin catheter through an artery in the leg or arm to engage the coronary arteries. X-ray dye (contrast medium) is then injected into the coronary artery through a portal in the catheter, which makes the coronary arteries visible under X-ray, so that the position and size of the blockages in the coronary arteries can be identified. Each year in U.S.A., more than one million individuals with angina pectoris or heart attack undergo coronary angiographies for evaluation of such coronary artery blockages. Once the blocked arteries are identified, the physician and surgeons then decide upon the best method to treat them.
One of the medically accepted ways to deal with coronary arterial blockage is percutaneous transluminal coronary angioplasty (PTCA). In this procedure, cardiologists thread a balloon catheter into the blocked coronary artery and stretch it by inflating the balloon against the arterial plaques causing vascular blockage. The PTCA procedure immediately improves blood flow in the coronary arteries, relieves angina pectoris, and prevents heart attacks. Approximately 400,000 patients undergo PTCA each year in the U.S.
However, when the arterial blockages are severe or widespread, the angioplasty procedure may fail or cannot be performed. In these instances, coronary artery bypass graft (CABG) surgery is then typically performed. In such bypass surgery, surgeons typically harvest healthy blood vessels from another part of the body and use them as vascular grafts to bypass the blocked coronary arteries. Each vascular graft is surgically attached with one of its ends joined to the aorta and the other end joined to the coronary artery. Approximately 500,000 CABG operations are currently performed in the U.S. each year to relieve symptoms and improve survival from heart attack.
It is useful here to understand in depth what a coronary arterial bypass entails and demands both for the patient and for the cardiac surgeon. In a standard coronary bypass operation, the surgeon must first make a foot-long incision in the chest and split the breast bone of the patient. The operation requires the use of a heart-lung machine that keeps the blood circulating while the heart is being stopped and the surgeon places and attaches the bypass grafts. To stop the heart, the coronary arteries also have to be perfused with a cold potassium solution (cardioplegia). In addition, the body temperature of the patient is lowered by cooling the blood as it circulates through the heart-lung machine in order to preserve the heart and other vital organs. Then, as the heart is stopped and a heart-lung machine pumps oxygenated blood through the patient""s body, the surgeon makes a tiny opening into the front wall of the target coronary artery with a very fine knife (arteriotomy); takes a previously excised saphenous vein (a vein from a leg) or an internal mammary artery (an artery from the chest); and sews the previously excised blood vessel to the coronary artery.
The most common blood vessel harvested for use as a graft is the greater (long) saphenous vein, which is a long straight vein running from just inside the ankle bone to the groin. The greater saphenous vein provides a bypass conduit of the most desired size, shape, and length for use with coronary arteries. The other blood vessel frequently used as a bypass graft is the left or right internal mammary artery, which comes off the subclavian artery and runs alongside the undersurface of the breastbone (sternum). Typically, the internal mammary artery remains attached to the subclavian artery proximally (its upper part) but is freed up distally (its lower part); and it is then anastomosed to the coronary artery. However, the saphenous vein graft should be sewn not only to coronary artery but also to the aorta, since the excised vein is detached at both ends. Then, to create the anastomosis at the aorta, the ascending thoracic aorta is first partially clamped using a curved vascular clamp to occlude the proper segment of the ascending aorta; and a hole is then created through the front wall of the aorta to anchor the vein graft with sutures. The graft bypasses the blockage in the coronary artery and restores adequate blood flow to the heart. After completion of the grafting, the patient is taken off of the heart-lung machine and the patient""s heart starts beating again. Most of the patients can leave the hospital in about 6 days after the CABG procedure.
It will be noted that coronary artery bypass surgery is considered a more definitive method for treating coronary arterial disease because all kinds of obstructions cannot be treated by angioplasty, and because a recurrence of blockages in the coronary arteries even after angioplasty is not unusual. Also coronary artery bypass surgery usually provides for a longer patency of the grafts and the bypassed coronary arteries in comparison with the results of PTCA procedure. However, coronary artery bypass surgery is a far more complicated procedure, having need of a heart-lung machine and a stoppage of the heart. Also, it is clearly the more invasive procedure and is more expensive to perform than PTCA. Therefore, cardiac surgeons have recently developed an alternative to the standard bypass surgery, namely xe2x80x9cminimally invasive bypass operation (MIBO) in order to reduce the risks and the cost associated with CABG surgery. Also, the MIBO is performed without use of a heart-lung machine or the stopping of the heart.
There are several ways that minimally invasive coronary bypass surgeries are being done today. Some versions are modeled after the video-assisted, fiber-optic techniques developed previously for gallbladder and other general surgeries. Other techniques have modified decades-old methods to sew arterial grafts onto beating hearts without using heart-lung machines. In the new and most popular version of the minimally invasive coronary bypass operation, surgeons use a thoracoscope, a fiber-optic device that is similar to a laparoscope. Initially, a three-inch incision is made to the left of the breast bone through which the surgeons operate. Three additional one-inch incisions then are made to insert a video camera, knife, surgical stapler, and other instruments. In the first stage of the operation, surgeons prepare the internal mammary artery, which courses vertically behind the rib cage, while watching on a video monitor. The internal mammary artery is freed up distally and is then sewn to the left anterior descending coronary artery. The internal mammary artery thus supplies blood to the coronary artery in place of blocked circulation of the heart. The wall of the chest formerly served by the mammary artery picks up blood from elsewhere via collateral blood circulations.
As a bypass graft, the left internal mammary artery (LIMA) offers a number of advantages to the saphenous vein graft including higher patency rate; and anatomically, histologically and geometrically provides a more comparable graft than the saphenous vein graft. LIMA is particularly useful as a graft to the coronary arteries such as the left anterior descending, diagonal branches, and ramus intermedius arteries (which are located on the surface of the heart relatively close to the left internal mammary artery). However, there are several disadvantages associated with a CABG operation with a left internal mammary artery graft, which are as follows: (1) technically, this artery is more tedious to take down; (2) sometimes the left internal mammary artery is inadequate in size and length; (3) the operation is suitable only for the five percent of candidates for coronary artery bypass because only a single left internal mammary artery is available as a graft; (4) anatomically, the operation is limited mainly to the left anterior descending coronary artery because of its location ad length; and (5) the majority of patients need more than single vessel bypass surgery.
In comparison, coronary arteries as small as 1 mm in diameter can be revascularized by vein grafting; and the saphenous vein is longer, larger, and more accessible than the left internal mammary artery. Equally important, although the greater or lesser saphenous veins of the leg are preferred, the cephalic or basilic veins in the arm are available as alternatives when the leg veins in the patient are unavailable or are unsuitable. For these reasons, the vein graft has today become the standard conduit for myocardial revascularization.
There remains, however, a long-standing and continuing need for a bypass technique which would allow surgeons to perform multiple bypass procedures using vein grafts as vascular shunts in a minimally invasive way, and, in particular, the need remains for a simpler method to place more than one vein graft proximally to the aorta and distally to the coronary artery without using a heart-lung machine and without stopping the heart. If such a technique were to be created, it would be recognized as a major advance in bypass surgery and be of substantial benefit and advantage for the patient suffering from coronary artery disease.
The present invention has multiple aspects. A first aspect provides a catheter apparatus for creating a bypass on-demand between an unobstructed blood vessel and an obstructed blood vessel in-vivo using a graft segment as a conduit, said bypass catheter apparatus comprising:
a catheter suitable for introduction into and extension through the body in-vivo to a chosen site wherein an unobstructed blood vessel is in anatomic proximity to an obstruction lying within another blood vessel, said catheter being comprised of a hollow tube of fixed axial length having a proximal end, a distal end, and at least one internal lumen of predetermined diameter;
an obturator for on-demand introduction and passage through said catheter to a chosen site on the unobstructed blood vessel in-vivo, said obturator comprising
(a) a puncturing headpiece for puncture of and entry into the lumen of an unobstructed blood vessel,
(b) a perforating end tip on said puncturing headpiece to facilitate the perforation of a blood vessel wall at the chosen site in-vivo,
(c) an elongated shaft of fixed axial length integrated with said puncturing headpiece, said elongated shaft being configured for the carrying and transport of a graft segment within said internal lumen of said catheter to the chosen site on the unobstructed blood vessel in-vivo; and
a thermoelastic deformable cuff comprised of a prepared shape-memory alloy in a chosen extant configuration for positioning over said elongated shaft adjacent to said puncturing headpiece of said obturator together with a graft segment, said thermoelastic deformable cuff having a discrete medial portion and two discrete end portions
(i) wherein, prior to the perforation of the unobstructed blood vessel in-vivo by said puncturing headpiece of said obturator, said medial portion of said cuff has been engaged and joined to one end of the graft segment then carried by said elongated shaft of said obturator thereby forming an engaged medial cuff portion and two discrete non-engaged cuff end portions,
(ii) and wherein, after the perforation of the unobstructed blood vessel in-vivo by said puncturing headpiece of said obturator, one of said non-engaged cuff end portions is extended into the lumen of the unobstructed blood vessel, and becomes thermoelastically deformed in-situ within the lumen of the unobstructed blood vessel into a prepared memory-shaped end configuration, and is disposed in the prepared memory-shaped end configuration onto an interior surface of the unobstructed blood vessel,
(iii) and wherein, after the perforation of the unobstructed blood vessel in-vivo by said puncturing headpiece of said obturator, the other of said non-engaged cuff end portions is positioned adjacent an exterior surface of the unobstructed blood vessel, and becomes thermoelastically deformed in-situ adjacent the exterior surface of the unobstructed blood vessel into another prepared memory-shaped end configuration, and is disposed in the other prepared memory-shaped end configuration onto an exterior surface of the unobstructed blood vessel.
(iv) and whereby the end of the graft segment engaged by the medial portion of the cuff becomes secured to and placed in blood flow communication with the unobstructed blood vessel and serves as conduit means for bypassing an obstruction and restoring blood flow from the unobstructed blood vessel to an obstructed blood vessel.
A second aspect of the present invention provides a catheter apparatus for creating a bypass on-demand between an unobstructed blood vessel and an obstructed blood vessel in-vivo using a graft segment as a conduit, said bypass catheter apparatus comprising:
a catheter suitable for introduction into and extension through the body in-vivo to a chosen site wherein an unobstructed blood vessel is in anatomic proximity to an obstruction lying within another blood vessel, said catheter being comprised of a hollow tube of fixed axial length having a proximal end, a distal end, and at least one internal lumen of predetermined diameter;
an obturator for on-demand introduction and passage through said catheter to a chosen site on the unobstructed blood vessel in-vivo, said obturator comprising
(a) a puncturing headpiece for puncture of and entry into the lumen of an unobstructed blood vessel,
(b) a perforating end tip on said puncturing headpiece to facilitate the perforation of a blood vessel wall at the chosen site in-vivo,
(c) an elongated shaft of fixed axial length integrated with said puncturing headpiece, said elongated shaft being configured for the carrying and transport of a graft segment within said internal lumen of said catheter to the chosen site on the unobstructed blood vessel in-vivo;
an inflatable and deflatable on-demand balloon of prechosen configuration disposed adjacent to said puncturing headpiece on said elongated shaft of said obturator, the girth of said balloon in the deflated state being less than the internal diameter of the graft segment to be used as a conduit; and
a thermoelastic deformable cuff comprised of a prepared shape-memory alloy in an chosen extant configuration for positioning over said elongated shaft adjacent to said puncturing headpiece of said obturator together with a graft segment to be used as a conduit, said thermoelastic deformable cuff having a discrete medial portion and two discrete end portions
(i) wherein, prior to the perforation of the unobstructed blood vessel in-vivo by said puncturing headpiece of said obturator, said discrete medial portion of said cuff has been engaged and joined to one end of the graft segment then carried by said elongated shaft of said obturator thereby forming an engaged medial cuff portion and two discrete non-engaged cuff end portions,
(ii) and wherein, after the perforation of the unobstructed blood vessel in-vivo by said puncturing headpiece of said obturator, one of said non-engaged cuff end portions is extended into the lumen of the unobstructed blood vessel, and becomes thermoelastically deformed in-situ within the lumen of the unobstructed blood vessel into a prepared memory-shaped end configuration, and is disposed in the prepared memory-shaped end configuration onto an interior surface of the unobstructed blood vessel,
(iii) and wherein, after the perforation of the unobstructed blood vessel in-vivo by said puncturing headpiece of said obturator, the other of said non-engaged cuff end portions is positioned adjacent an exterior surface of the unobstructed blood vessel, and becomes thermoelastically deformed in-situ adjacent the exterior surface of the unobstructed blood vessel into another prepared memory-shaped end configuration, and is disposed in the other prepared memory-shaped end configuration onto an exterior surface of the unobstructed blood vessel,
(iv) and whereby the end of the graft segment engaged by the medial portion of the cuff becomes secured to and placed in blood flow communication with the unobstructed blood vessel and serves as conduit means for bypassing an obstruction and restoring blood flow from the unobstructed blood vessel to an obstructed blood vessel.